Devices to assist individuals with impaired mobility due to illness or injury include passive and active assistance and support devices, mobility devices and strength training devices. Passive assistance and support devices, such as canes, crutches, walkers and manual wheelchairs, provide assistance with mobility. However, individuals using such devices must supply all of the power needed by exerting forces with other muscles to compensate for the muscle that is weak or injured. Additionally, many passive assistance and support devices provide limited mobility.
Many types of existing passive knee braces are available for stabilizing the knee to prevent or recover from injury, or to provide stability for chronic conditions. Existing braces typically come in either a few standard sizes or are custom-fitted to each patient. The standard sizes often cannot conform closely to the unique shape of an individual leg and may suffer from poor fit. The custom-fitted braces are expensive and cannot be re-used by other patients after the brace is no longer needed. Both types of brace typically rely on the tightness of fit to keep them from sliding down the leg. Keeping these braces in the proper position is a largely unmet problem.
Existing orthotic designs have many points of structural contact with the subject's body. Each contact point must be custom molded to a specific shape to meet the wide array of dimensions and geometries of subjects. Otherwise, the points of contact will be sub-optimal and will result in discomfort and pain. Additionally, existing knee braces have not been designed to couple with actuators to provide active assistance. Most passive braces do not have the required structure or attachment points to allow an actuator to be coupled.
Moreover, existing devices such as continuous passive motion (CPM) machines and robotic therapy devices involve the use of an external force to flex and extend a subject's limb to induce motion. Continuous passive motion of a joint following injury, illness or surgery has been found to reduce the post-operative pain, decrease adhesions, decrease muscle atrophy, and enhance the speed of recovery, while minimizing various risks of mobilization. CPM machines slowly and gently move a subject's leg through a reciprocal cycle between a flexion position in which an angle between the subject's femur and tibia is at a minimum, and an extension in position in which the angle between the subject's femur and the tibia is at a maximum. However, CPM machines are not sufficiently small and light as to allow attachment directly to a subject's leg (or other body part) and do not allow for mobility, typically requiring the subject to be in the reclined or sitting position during operation.